Problem: Constraints

* H is an integer between 2 and 50 (inclusive).
* W is an integer between 2 and 50 (inclusive).
* s_{i, j} is `.` or `#` (1 \leq i \leq H, 1 \leq j \leq W).
* s_{1, 1} and s_{H, W} are `.`.

Input

Input is given from Standard Input in the following format:


H W
s_{1, 1}s_{1, 2}s_{1, 3} ... s_{1, W}
s_{2, 1}s_{2, 2}s_{2, 3} ... s_{2, W}
:   :
s_{H, 1}s_{H, 2}s_{H, 3} ... s_{H, W}


Output

Print the maximum possible score that Snuke can achieve, or print -1 if the game cannot be completed.

Examples

Input

3 3
..#
#..
...


Output

2


Input

3 3
..#
..
...


Output

2


Input

10 37
.....................................
...#...####...####..###...###...###..
..#.#..#...#.##....#...#.#...#.#...#.
..#.#..#...#.#.....#...#.#...#.#...#.
.#...#.#..##.#.....#...#.#.###.#.###.
.#####.####..#.....#...#..##....##...
.#...#.#...#.#.....#...#.#...#.#...#.
.#...#.#...#.##....#...#.#...#.#...#.
.#...#.####...####..###...###...###..
.....................................


Output

209

Solution (in CPP):

Solution:
#include<iostream>
#include<map>
#include<queue>
using namespace std;
typedef pair<int,int> P;
char F[51][51];
int C[51][51];
int x[4]={1,0,-1,0};
int y[4]={0,1,0,-1};
int white=0;
queue<P> Q;

void bfs(int h,int w){
  C[1][1]=1;
  Q.push(P{1,1});
  while(!Q.empty()){
    P p=Q.front(); Q.pop();
    if(p.first==h&&p.second==w) break;
    for(int i=0;i<4;i++){
      int nx=p.first+x[i];
      int ny=p.second+y[i];
      if(nx>0&&nx<=w&&ny>0&&ny<=h&&F[ny][nx]=='.'){
        F[ny][nx]='#';
        C[ny][nx]=C[p.second][p.first]+1;
        Q.push(P{nx,ny});
      }
    }
  }
}
int main(){
  int h,w;
  cin>>h>>w;
  for(int i=1;i<=h;i++){
    for(int j=1;j<=w;j++){
      cin>>F[i][j];
      if(F[i][j]=='.') white++;
      C[i][j]=0;
    }
  }

  bfs(h,w);
  if(C[h][w]==0) cout<<-1<<"\n";
  else cout<<white-C[h][w]<<"\n";

}